1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine or a printer, and particularly to improvements of such a type of image forming apparatus that a sheet supply unit is disposed in parallel with an image forming unit, and a sheet supply unit for use in the image forming apparatus.
2. Description of the Related Art
In connection with requirements of coloring, high-speed operation, increase of lifetime, etc. to image forming apparatuses, there has been recently such a tendency that some of image forming modules accommodated in an image forming unit, for example, a developing portion and a transfer portion are increased in size and the dimensional occupational ratio of these portions in the height direction of the image forming apparatus is increasing.
Under such a situation, the position at which an image transfer operation is carried out on a recording sheet by the image forming modules (hereinafter referred to as “transfer position”) is shifted to a lower position, and thus a sheet feeding path must be located at a lower position of the apparatus.
Further, a sheet supply portion is ordinarily provided by using a space below the image forming modules. However, when the image forming modules themselves are large in size, it is impossible to dispose multiple sheet supply trays as the sheet supply portion below the image forming modules.
That is, if the multiple sheet supply trays are disposed as in the past regardless of the large size of the image forming modules, the relative position of the image forming modules is high and thus the height dimension of the image forming unit itself must be set to a large value. Therefore, there occurs such a problem that the operating portion of the image forming unit must be located at such a position that it is difficult for a user to manipulate the operating portion.
Conversely, when the operating portion of the image forming unit is located at a position which is suitable for user's manipulation, the space below the image forming modules is necessarily narrow, so that it is substantially difficult to dispose a large-capacity sheet supply tray as the sheet supply portion.
In order to solve these technical problems, there has been proposed a technique in which a sheet supply unit having multiple sheet supply trays accommodated therein is disposed at the side of the image forming unit so as to be in parallel with the image forming unit at the side thereof (see Japanese Laid-open Patent Application No. Hei-3-182431).
However, in this type of technique, recording sheets in the sheet supply trays are fed out in the same sheet feed-out direction from the image forming unit side. That is, the same sheet feed-out direction is set for all the sheet supply trays. Therefore, sheet feeding paths extending from the respective sheet supply trays are concentratively disposed at the image forming unit side of the respective sheet supply trays in the sheet supply unit, and then the recording sheets are fed out from the sheet feed-out port of the sheet supply unit to the image forming unit side.
In this case, from the viewpoint of reducing the size of the apparatus at maximum, the space between the sheet supply trays and the image forming unit side wall surface of the sheet supply unit is originally set to be narrow, and thus if the sheet feeding paths from the respective sheet supply units are concentratively disposed, not only a mechanism for jam clearance in the sheet feeding paths is more complicated, but also an operation for the jam clearance is more cumbersome.
In order to solve this technical problem, it may be considered that the sheet supply unit is moved away from the image forming unit in the jam clearance process or the like to ensure a working space for the jam clearance or the like. However, from the viewpoint of workability of the jam clearance, it is not preferable that the sheet supply unit having a large weight is moved every time the jam clearance is carried out.